Small Engines (Lawn Mowers, etc.): engine, carb settings, gas flow

Question
Hi Matt,
I have a 13.5 horse BS engine that runs high low as if being regulated by the governor, under load or not. This thing is nearly new.

Answer
surging is usualy a cause of the governer arm that is attached to the samll shaft of the governer gear that comes out of the side of the engine being out of adjustment. you could have hit it or it may have worked itself loose. ther could be other reasons for the surging due to carb problems, or gas flow, but i check the gov. first. When the engine is off all the carb linkage and carb settings are at full speed when the motor starts the arm pulls the carb linkage to slow down the engine and keep it from over reving. while the engine is off loosen the nut on the arm and with a pair of pliers twist the shaft towards the carb then retighten the nut while holing it (the shaft) with a pair of pliers. in some cases it may not even feel like it moved but it only takes a small amount to throw it off. this is how it works on the walk behinds anyways hope this helps